High toughness ultra-fine grain cemented carbide numerical control blade and its preparation process

Abstract

The present application relates to the technical field of alloy, in particular to a kind of high strength and toughness ultra-fine grain hard alloy numerical control blade and its preparation process.The blade matrix is made of specific proportion of composite modified ultra-fine tungsten carbide powder, cobalt powder, vanadium carbide, chromium carbide and graphite powder.The preparation process includes that after activation treatment to ultra-fine tungsten carbide powder, sequentially carry out iron-based enrichment inner layer construction, ammonium metavanadate interface treatment and nickel-based enrichment outer layer construction, obtain composite modified powder, then step-by-step mixing, pressing, multi-stage temperature sintering and edge treatment.The process effectively coordinates the relationship of grain growth, interface bonding and densification through the synergistic effect of orderly component construction, step-by-step addition of inhibitor and optimized sintering curve, so that the blade has high strength, high toughness and excellent wear resistance.

Description

Technical Field

[0001] This invention relates to the field of alloy technology, and in particular to a high-strength, high-toughness, ultra-fine-grained cemented carbide CNC cutting tool and its manufacturing process. Background Technology

[0002] As a core component of modern high-efficiency machining, cemented carbide CNC inserts directly determine cutting efficiency, machining accuracy, and stability. To meet the demands of machining high-strength, high-precision materials, ultrafine-grained WC-Co cemented carbide has become a research hotspot due to its excellent hardness and wear resistance. However, with the continuous refinement of WC grain size, the grain boundary area increases dramatically, and the problems of abnormal grain growth and uneven distribution of the binder phase during sintering become increasingly prominent, directly restricting the improvement of the alloy's overall performance.

[0003] In existing technologies, single or composite grain growth inhibitors, such as vanadium carbide and chromium carbide, are typically added to the mixture to delay grain growth. However, in ultrafine powder systems, the uniform distribution of the inhibitor in the matrix is ​​a technical challenge. Inhibitors applied in a single premix often agglomerate locally during subsequent ball milling and mixing, resulting in uneven pinning of grain boundaries during sintering. Insufficient inhibition in some areas leads to abnormal grain growth, while in others, excessive accumulation of inhibitors forms brittle phases, which become crack initiation sites. Consequently, while the alloy achieves high hardness, its transverse fracture strength and impact toughness decrease, making it unsuitable for high-load or semi-interrupted cutting conditions.

[0004] To address the interfacial bonding issue, existing technologies have attempted to pre-coat the WC powder surface with transition metals (such as nickel and iron) to improve wettability with the cobalt binder phase and enhance interfacial bonding. However, conventional co-precipitation or electroless plating methods often struggle to precisely control the morphology, thickness, and compositional gradient of the coating layer on the surface of ultrafine WC particles, and even more so to achieve the spatiotemporal ordered distribution of different functional elements. For example, if iron and nickel are not properly coated, they can easily diffuse excessively into the binder phase during subsequent sintering, altering their intrinsic properties or reacting adversely with inhibitors, thus weakening the effect of inhibiting grain growth.

[0005] Furthermore, in terms of sintering processes, higher sintering temperatures and longer holding times are typically used to achieve high densification. However, in ultrafine-grained systems, prolonged high-temperature holding easily induces rapid grain coarsening, while excessively rapid heating or cooling to maintain grain size can lead to insufficient densification and defects such as porosity. The single sintering curves used in existing technologies are insufficient to reconcile the contradictions between ultrafine grain stability, high densification, and ideal microstructure. Therefore, developing a process for preparing ultrafine-grained cemented carbide cutting tools that can synergistically control grain growth, optimize interface structure, and simultaneously improve strength and toughness has become a pressing problem in this field. Summary of the Invention

[0006] In view of this, the purpose of this invention is to propose a high-strength and tough ultrafine-grained cemented carbide CNC cutting tool and its preparation process, so as to solve the problems of uneven distribution of grain inhibitors, difficulty in controlling interface bonding, and difficulty in achieving both grain size and density under high-temperature sintering in the preparation process of existing ultrafine-grained cemented carbide.

[0007] To achieve the above objectives, the present invention provides a high-strength and tough ultrafine-grained cemented carbide CNC cutting tool, comprising a cutting tool matrix made of high-strength and tough ultrafine-grained cemented carbide material; by mass parts, the high-strength and tough ultrafine-grained cemented carbide material is prepared from the following raw materials: 500 parts of ultrafine tungsten carbide powder with an average particle size of 80-150 nm as the matrix, which is first activated to form an iron-based enriched inner layer and then treated with ammonium metavanadate to form a nickel-based enriched outer layer to obtain a composite modified ultrafine tungsten carbide powder, 40-50 parts of cobalt powder, 0.35-0.70 parts of vanadium carbide, 1.2-1.8 parts of chromium carbide and 0.3-0.5 parts of graphite powder.

[0008] Preferably, the activation is carried out using an acid-ammonium fluoride system activation solution composed of hydrofluoric acid, nitric acid and ammonium fluoride.

[0009] Preferably, the activation solution is prepared by mixing deionized water, hydrofluoric acid with a mass fraction of 40%, nitric acid with a mass fraction of 65%, and ammonium fluoride in a ratio of 1900-2200mL:55-70mL:35-50mL:5-8g.

[0010] Preferably, the composite modified ultrafine tungsten carbide powder is prepared from the following raw materials: based on 500 parts of ultrafine tungsten carbide powder with an average particle size of 80-150 nm, 12-18 parts of ferric nitrate nonahydrate, 0.4-0.8 parts of ammonium metavanadate and 20-28 parts of nickel nitrate hexahydrate are added.

[0011] Preferably, the cobalt powder has an average particle size of 350 nm, the vanadium carbide has an average particle size of 1.5 μm, the chromium carbide has an average particle size of 1.2 μm, and the graphite powder has an average particle size of 1.4 μm.

[0012] Preferably, the CNC cutting tool undergoes edge passivation treatment, with a passivation amount of 12-20 μm.

[0013] Furthermore, the present invention also provides a manufacturing process for a high-strength, high-toughness, ultra-fine-grained cemented carbide CNC cutting tool, comprising the following steps:

[0014] S1. Activate the ultrafine tungsten carbide powder to obtain activated tungsten carbide powder;

[0015] S2. The activated tungsten carbide powder is deposited with an iron source and reduced to obtain a pre-coated powder with an iron-based enriched inner layer on the surface.

[0016] S3. The pre-coated powder is treated with ammonium metavanadate, then nickel source is deposited and reduced to obtain the composite modified ultrafine tungsten carbide powder.

[0017] S4. The composite modified ultrafine tungsten carbide powder is mixed with vanadium carbide and then subjected to low-energy ball milling. After drying, it is mixed with cobalt powder, chromium carbide and graphite powder, wet-milled, dried and granulated to obtain pressed material.

[0018] S5. After pressing the material into a blade blank, sinter it, and then grind and passivate the sintered blade to obtain a high-strength and tough ultra-fine grain cemented carbide CNC blade.

[0019] Preferably, the reduction in step S2 is as follows: first, the temperature is raised to 190-220°C at 2°C / min under a nitrogen atmosphere and held for 20-25 min, then the temperature is switched to a hydrogen atmosphere and raised to 370-400°C and held for 35-50 min.

[0020] Preferably, the reduction in step S3 is as follows: first, the temperature is raised to 190-220°C at 2°C / min under a nitrogen atmosphere and held for 20-25 min, then the temperature is switched to a hydrogen atmosphere and raised to 410-440°C and held for 45-60 min.

[0021] Preferably, in step S4, the low-energy ball milling time is 0.8-1.5h, the ball-to-material ratio is 2-4:1, and the rotation speed is 110-140r / min; the wet milling time is 5-8h, the ball-to-material ratio is 5-6:1, and the rotation speed is 170-200r / min.

[0022] Preferably, in step S5, during pressing, the material is first pre-pressed at 70-100MPa, then finally pressed at 170-210MPa and held for 25-40s; during sintering, the temperature is increased according to the following regime under a vacuum degree not higher than 5Pa: 200℃ for 1h, 480℃ for 1h, 620℃ for 1h, 900℃ for 25-35min, 1270-1290℃ for 12-20min, and then increased to 1380-1400℃ for 35-45min.

[0023] This invention activates ultrafine tungsten carbide powder with an acid-ammonium fluoride system, creating abundant defect sites on its surface. This provides an ideal reaction basis for the subsequent stepwise construction of functional layers and effectively enhances the bonding strength between the matrix and the modified layer.

[0024] On an activated matrix, an iron-based enriched inner layer is first constructed, followed by the introduction of ammonium metavanadate for interface treatment, and finally a nickel-based enriched outer layer is formed. This "iron-vanadium-nickel" construction strategy allows iron to improve the surface activity of tungsten carbide in advance, ammonium metavanadate to form effective early pinning at the interface, and the nickel outer layer to serve as a good transition to the subsequent cobalt binder phase. This achieves the ordered spatial distribution and functional synergy of different functional elements and optimizes the network continuity of the final binder phase.

[0025] Using ammonium metavanadate as the initial vanadium source, along with the later addition of vanadium carbide, constitutes a two-stage vanadium supply mechanism. Ammonium metavanadate focuses on creating a site-occupying effect at the tungsten carbide / binder phase interface, suppressing rapid grain growth caused by interfacial reactions; while the subsequent vanadium carbide plays a short-range diffusion suppression role in a wider grain boundary region. This temporal and spatial division of labor between the two synergistically achieves more precise and comprehensive control over grain size, avoiding the brittleness that may be caused by excessively high local concentrations of a single vanadium source.

[0026] Adding chromium carbide later, during wet milling with cobalt powder, allows it to act more effectively on the outer regions of the binder phase and grain boundary junctions. This delayed addition allows it to exert a more effective dragging effect on grain boundaries in the later stages of sintering, promoting rounded grain morphology, reducing stress concentration at sharp corners, and thus significantly improving the cutting tool's resistance to chipping under impact loads. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0028] Example 1:

[0029] Step 1: Weigh 500g of ultrafine tungsten carbide powder (average particle size 100nm), divide it into 5 equal portions of 100g each, and add each portion to an activation solution prepared with 2000mL of deionized water, 60mL of 40% hydrofluoric acid, 40mL of 65% nitric acid, and 6g of ammonium fluoride. Sonicate at 20℃ for 6min, then mechanically stir for 8min. Immediately filter the solution and wash it with deionized water until the pH of the filtrate is 6.5. Replace the water with 300mL of anhydrous ethanol and vacuum dry at 60℃ for 6h. Combine the 5 batches of activated tungsten carbide powder to obtain activated tungsten carbide powder with defect sites on the surface.

[0030] Step 2: Add all the activated tungsten carbide powder obtained in Step 1 to a mixture of 3000 mL deionized water and 1500 mL anhydrous ethanol. At 40 °C, add 10 g of citric acid monohydrate and 15 g of sodium citrate dihydrate sequentially and stir for 20 min. Separately, dissolve 15 g of ferric nitrate nonahydrate in 300 mL of deionized water and add it dropwise over 30 min. Then, add 10% ammonia solution dropwise over 40 min until the pH of the system reaches 7.7. Continue stirring and maintaining the temperature for 45 min. After filtration, wash once each with 500 mL of deionized water and 500 mL of anhydrous ethanol, and dry at 80 °C for 8 h. After drying, first heat to 200 °C at 2 °C / min under a nitrogen atmosphere and hold for 20 min, then switch to a hydrogen atmosphere and heat to 380 °C and hold for 40 min to obtain pre-coated powder.

[0031] Step 3: Add all the pre-coated powder obtained in Step 2 to a mixture of 3500 mL deionized water and 1000 mL anhydrous ethanol; add 0.6 g ammonium metavanadate to 120 mL deionized water, heat to 70°C, and then add 1 mL of 25% ammonia solution dropwise until completely dissolved. Add the suspension over 10 min and continue stirring for 30 min; separately dissolve 24 g nickel nitrate hexahydrate and 12 g sodium citrate dihydrate in 300 mL deionized water, and heat to 40°C. The addition was completed within min, and then 10% ammonia water was slowly added dropwise over 50 min until the pH of the system reached 8.7. The system was then kept at 50℃ for 60 min. After filtration, the system was washed once each with 500 mL of deionized water and 500 mL of anhydrous ethanol, and dried at 80℃ for 8 h. After drying, the system was first heated to 200℃ at 2℃ / min under a nitrogen atmosphere and kept at that temperature for 20 min, and then switched to a hydrogen atmosphere and heated to 420℃ and kept at that temperature for 50 min to obtain the composite modified powder.

[0032] Step 4: Mix all the composite modified powder obtained in Step 3 with 0.5g vanadium carbide (average particle size 1.5μm) and 800mL anhydrous ethanol, and ball mill with cemented carbide balls for 1h at a ball-to-material ratio of 3:1 and a rotation speed of 120r / min. After ball milling, dry under reduced pressure at 60℃ for 4h, then add it to a ball mill jar with 45g cobalt powder (average particle size 350nm), 1.5g chromium carbide (average particle size 1.2μm), 0.4g graphite powder (average particle size 1.4μm), 8g paraffin wax No. 58, 3g polyethylene glycol 4000 and 600mL anhydrous ethanol. Wet mill with cemented carbide balls for 6h at a ball-to-material ratio of 5:1 and a rotation speed of 180r / min. After ball milling, dry under reduced pressure at 55℃, and granulate through a 60-mesh sieve to obtain the pressed material.

[0033] Step 5: Press the pressed material obtained in Step 4 into a CNC turning tool blank. First, pre-press it at 80MPa, then final press it at 180MPa and hold the pressure for 30s. Then place it in a vacuum sintering furnace and heat it according to the following schedule under a vacuum degree not higher than 5Pa: 200℃ for 1h, 480℃ for 1h, 620℃ for 1h, 900℃ for 30min, 1280℃ for 15min; then heat it to 1390℃ and hold it for 40min to complete sintering. Then cool it with the furnace. Perform conventional grinding and edge passivation on the sintered tool. The edge passivation amount is controlled to be 15μm to obtain a high-strength and tough ultra-fine grain cemented carbide CNC tool.

[0034] Example 2:

[0035] Step 1: Weigh 500g of ultrafine tungsten carbide powder (average particle size 100nm), divide it into 5 equal portions of 100g each, and add each portion to an activation solution prepared with 1900mL of deionized water, 55mL of 40% hydrofluoric acid, 35mL of 65% nitric acid, and 5g of ammonium fluoride. Sonicate at 18℃ for 5min, then mechanically stir for 7min. Immediately filter the solution and wash it with deionized water until the pH of the filtrate is 6.8. Replace the water with 280mL of anhydrous ethanol and vacuum dry at 55℃ for 5h. Combine the 5 batches of activated tungsten carbide powder to obtain activated tungsten carbide powder with defect sites on the surface.

[0036] Step 2: Add all the activated tungsten carbide powder obtained in Step 1 to a mixture of 3000 mL deionized water and 1300 mL anhydrous ethanol. At 38 °C, add 9 g of citric acid monohydrate and 13 g of sodium citrate dihydrate sequentially and stir for 20 min. Separately, dissolve 12 g of ferric nitrate nonahydrate in 250 mL of deionized water and add it dropwise over 35 min. Then, add 10% ammonia solution dropwise over 35 min until the pH of the system reaches 7.5. Continue stirring and maintaining the temperature for 40 min. After filtration, wash once with 500 mL of deionized water and once with 500 mL of anhydrous ethanol, and dry at 78 °C for 7 h. After drying, first heat to 190 °C at 2 °C / min under a nitrogen atmosphere and hold for 20 min, then switch to a hydrogen atmosphere and heat to 370 °C and hold for 35 min to obtain pre-coated powder.

[0037] Step 3: Add all the pre-coated powder obtained in Step 2 to a mixture of 3300 mL deionized water and 900 mL anhydrous ethanol; add 0.4 g ammonium metavanadate to 100 mL deionized water, heat to 68 °C, and then add 0.8 mL of 25% ammonia solution dropwise until completely dissolved. Add the suspension over 8 min and continue stirring for 25 min; separately dissolve 20 g nickel nitrate hexahydrate and 10 g sodium citrate dihydrate in 260 mL deionized water, and heat to 35 °C. The addition was completed within min, and then 10% ammonia water was slowly added dropwise over 45 min until the pH of the system reached 8.5. The system was then kept at 48℃ for 50 min. After filtration, the system was washed once each with 500 mL of deionized water and 500 mL of anhydrous ethanol, and dried at 78℃ for 7 h. After drying, the system was first heated to 190℃ at 2℃ / min under a nitrogen atmosphere and kept at that temperature for 20 min, and then heated to 410℃ under a hydrogen atmosphere and kept at that temperature for 45 min to obtain the composite modified powder.

[0038] Step 4: Mix all the composite modified powder obtained in Step 3 with 0.35g of vanadium carbide (average particle size 1.5μm) and 750mL of anhydrous ethanol. Perform low-energy ball milling for 0.8h using cemented carbide balls at a ball-to-material ratio of 3:1 and a rotation speed of 110r / min. After ball milling, dry under reduced pressure at 58℃ for 4h. Then, add the mixture to a ball mill jar along with 42g of cobalt powder (average particle size 350nm), 1.2g of chromium carbide (average particle size 1.2μm), 0.3g of graphite powder (average particle size 1.4μm), 7g of paraffin wax, 2.5g of polyethylene glycol, and 550mL of anhydrous ethanol. Wet mill using cemented carbide balls for 5h at a ball-to-material ratio of 5:1 and a rotation speed of 170r / min. After ball milling, dry under reduced pressure at 52℃ and granulate through a 60-mesh sieve to obtain the pressed material.

[0039] Step 5: Press the pressed material obtained in Step 4 into a CNC turning tool blank. First, pre-press it at 70MPa, then final press it at 170MPa and hold the pressure for 25s. Then place it in a vacuum sintering furnace and heat it according to the following schedule under a vacuum degree not higher than 5Pa: 200℃ for 1h, 480℃ for 1h, 620℃ for 1h, 900℃ for 25min, 1270℃ for 12min; then heat it to 1380℃ and hold it for 45min to complete sintering. Then cool it with the furnace. Perform conventional grinding and edge passivation on the sintered tool. The edge passivation amount is controlled to be 12μm to obtain a high-strength and tough ultra-fine grain cemented carbide CNC tool.

[0040] Example 3:

[0041] Step 1: Weigh 500g of ultrafine tungsten carbide powder (average particle size 100nm), divide it into 5 equal portions of 100g each, and add each portion to an activation solution prepared with 2100mL of deionized water, 65mL of 40% hydrofluoric acid, 45mL of 65% nitric acid, and 7g of ammonium fluoride. Sonicate at 22℃ for 7min, then mechanically stir for 9min. Immediately filter the solution and wash it with deionized water until the pH of the filtrate is 6.9. Replace the water with 320mL of anhydrous ethanol and vacuum dry at 65℃ for 7h. Combine the 5 batches of activated tungsten carbide powder to obtain activated tungsten carbide powder with defect sites on the surface.

[0042] Step 2: Add all the activated tungsten carbide powder obtained in Step 1 to a mixture of 3200 mL deionized water and 1600 mL anhydrous ethanol. At 42 °C, add 11 g of citric acid monohydrate and 17 g of sodium citrate dihydrate sequentially and stir for 20 min. Separately, dissolve 18 g of ferric nitrate nonahydrate in 350 mL of deionized water and add it dropwise over 45 min. Then, add 10% ammonia solution dropwise over 45 min until the pH of the system reaches 7.9. Continue stirring and maintaining the temperature for 50 min. After filtration, wash once with 500 mL of deionized water and once with 500 mL of anhydrous ethanol, and dry at 82 °C for 9 h. After drying, first heat to 210 °C at 2 °C / min under a nitrogen atmosphere and hold for 20 min, then switch to a hydrogen atmosphere and heat to 395 °C and hold for 45 min to obtain pre-coated powder.

[0043] Step 3: Add all the pre-coated powder obtained in Step 2 to a mixture of 3700 mL deionized water and 1100 mL anhydrous ethanol; add 0.8 g ammonium metavanadate to 140 mL deionized water, heat to 72°C, and then add 1.2 mL of 25% ammonia solution dropwise until completely dissolved. Add the suspension over 12 min and continue stirring for 35 min; separately dissolve 28 g nickel nitrate hexahydrate and 14 g sodium citrate dihydrate in 340 mL deionized water, and heat to 4°C. The addition was completed within 5 minutes, and then 10% ammonia solution was slowly added dropwise over 55 minutes until the pH of the system reached 8.9. The system was then kept at 52°C for 70 minutes. After filtration, the system was washed once each with 500 mL of deionized water and 500 mL of anhydrous ethanol, and dried at 82°C for 9 hours. After drying, the system was first heated to 210°C at a rate of 2°C / min under a nitrogen atmosphere and kept at that temperature for 20 minutes. Then, the system was switched to a hydrogen atmosphere and heated to 435°C and kept at that temperature for 55 minutes to obtain the composite modified powder.

[0044] Step 4: Mix all the composite modified powder obtained in Step 3 with 0.70g vanadium carbide (average particle size 1.5μm) and 850mL anhydrous ethanol, and ball mill with cemented carbide balls for 1.2h at a ball-to-material ratio of 4:1 and a rotation speed of 130r / min. After ball milling, dry under reduced pressure at 62℃ for 5h, then add it to a ball mill jar along with 48g cobalt powder (average particle size 350nm), 1.8g chromium carbide (average particle size 1.2μm), 0.5g graphite powder (average particle size 1.4μm), 9g paraffin wax, 3.5g polyethylene glycol, and 650mL anhydrous ethanol. Wet mill with cemented carbide balls for 7h at a ball-to-material ratio of 6:1 and a rotation speed of 190r / min. After ball milling, dry under reduced pressure at 56℃, and granulate through a 60-mesh sieve to obtain the pressed material.

[0045] Step 5: Press the pressed material obtained in Step 4 into a CNC turning tool blank. First, pre-press it at 90MPa, then final press it at 200MPa and hold it for 35s. Then place it in a vacuum sintering furnace and heat it according to the following schedule under a vacuum degree not higher than 5Pa: 200℃ for 1h, 480℃ for 1h, 620℃ for 1h, 900℃ for 35min, 1290℃ for 18min; then heat it to 1400℃ for 38min to complete sintering. Then cool it with the furnace. Perform conventional grinding and edge passivation on the sintered tool. The edge passivation amount is controlled to be 18μm to obtain a high-strength and tough ultra-fine grain cemented carbide CNC tool.

[0046] Example 4:

[0047] Step 1: Weigh 500g of ultrafine tungsten carbide powder (average particle size 100nm), divide it into 5 equal portions of 100g each, and add each portion to an activation solution prepared with 2000mL of deionized water, 60mL of 40% hydrofluoric acid, 50mL of 65% nitric acid, and 6g of ammonium fluoride. Sonicate at 20℃ for 6min, then mechanically stir for 8min. Immediately filter the solution and wash it with deionized water until the pH of the filtrate is 6.3. Replace the water with 300mL of anhydrous ethanol and vacuum dry at 60℃ for 6h. Combine the 5 batches of activated tungsten carbide powder to obtain activated tungsten carbide powder with defect sites on the surface.

[0048] Step 2: Add all the activated tungsten carbide powder obtained in Step 1 to a mixture of 2800 mL deionized water and 1700 mL anhydrous ethanol. At 40 °C, add 10 g of citric acid monohydrate and 15 g of sodium citrate dihydrate sequentially and stir for 20 min. Separately, dissolve 16 g of ferric nitrate nonahydrate in 300 mL of deionized water and add it dropwise over 40 min. Then, add 10% ammonia solution dropwise over 40 min until the pH of the system reaches 7.8. Continue stirring and maintaining the temperature for 45 min. After filtration, wash once with 500 mL of deionized water and once with 500 mL of anhydrous ethanol, and dry at 80 °C for 8 h. After drying, first heat to 200 °C at 2 °C / min under a nitrogen atmosphere and hold for 20 min, then switch to a hydrogen atmosphere and heat to 385 °C and hold for 40 min to obtain pre-coated powder.

[0049] Step 3: Add all the pre-coated powder obtained in Step 2 to a mixture of 3600 mL deionized water and 1000 mL anhydrous ethanol; add 0.5 g ammonium metavanadate to 110 mL deionized water, heat to 70°C, and then add 1.0 mL of 25% ammonia solution dropwise until completely dissolved. Add the suspension over 10 min and continue stirring for 30 min; separately dissolve 26 g nickel nitrate hexahydrate and 13 g sodium citrate dihydrate in 320 mL deionized water, and then... The addition was completed within 0 min, and then 10% ammonia solution was slowly added dropwise over 50 min until the pH of the system reached 8.6. The system was then kept at 50℃ for 60 min. After filtration, the system was washed once each with 500 mL of deionized water and 500 mL of anhydrous ethanol, and dried at 80℃ for 8 h. After drying, the system was first heated to 200℃ at 2℃ / min under a nitrogen atmosphere and kept at that temperature for 20 min, and then heated to 425℃ under a hydrogen atmosphere and kept at that temperature for 50 min to obtain the composite modified powder.

[0050] Step 4: Mix all the composite modified powder obtained in Step 3 with 0.45g vanadium carbide (average particle size 1.5μm) and 800mL anhydrous ethanol, and ball mill with cemented carbide balls for 1.0h at a ball-to-material ratio of 3:1 and a rotation speed of 120r / min. After ball milling, dry under reduced pressure at 60℃ for 4h, then add it to a ball mill jar with 40g cobalt powder (average particle size 350nm), 1.6g chromium carbide (average particle size 1.2μm), 0.35g graphite powder (average particle size 1.4μm), 8g paraffin wax, 3g polyethylene glycol and 600mL anhydrous ethanol. Wet mill with cemented carbide balls for 6h at a ball-to-material ratio of 5:1 and a rotation speed of 180r / min. After ball milling, dry under reduced pressure at 55℃, and granulate through a 60-mesh sieve to obtain the pressed material.

[0051] Step 5: Press the pressed material obtained in Step 4 into a CNC turning tool blank. First, pre-press it at 80MPa, then final press it at 185MPa and hold the pressure for 30s. Then place it in a vacuum sintering furnace and heat it according to the following schedule under a vacuum degree not higher than 5Pa: 200℃ for 1h, 480℃ for 1h, 620℃ for 1h, 900℃ for 30min, 1285℃ for 20min; then heat it to 1395℃ for 35min to complete sintering. Then cool it with the furnace. Perform conventional grinding and edge passivation on the sintered tool. The edge passivation amount is controlled to be 14μm to obtain a high-strength and tough ultra-fine grain cemented carbide CNC tool.

[0052] Example 5:

[0053] Step 1: Weigh 500g of ultrafine tungsten carbide powder (average particle size 100nm), divide it into 5 equal portions of 100g each, and add each portion to an activation solution prepared with 2200mL of deionized water, 70mL of 40% hydrofluoric acid, 40mL of 65% nitric acid, and 8g of ammonium fluoride. Sonicate at 25℃ for 8min, then mechanically stir for 10min. Immediately filter the solution and wash it with deionized water until the pH of the filtrate is 6.8. Replace the water with 350mL of anhydrous ethanol and vacuum dry at 70℃ for 8h. Combine the 5 batches of activated tungsten carbide powder to obtain activated tungsten carbide powder with defect sites on the surface.

[0054] Step 2: Add all the activated tungsten carbide powder obtained in Step 1 to a mixture of 3500 mL deionized water and 1500 mL anhydrous ethanol. At 45 °C, add 12 g of citric acid monohydrate and 18 g of sodium citrate dihydrate sequentially and stir for 20 min. Separately, dissolve 14 g of ferric nitrate nonahydrate in 320 mL of deionized water and add it dropwise over 40 min. Then, add 10% ammonia solution dropwise over 50 min until the pH of the system reaches 7.6. Continue stirring and maintaining the temperature for 60 min. After filtration, wash once with 500 mL of deionized water and once with 500 mL of anhydrous ethanol, and dry at 85 °C for 10 h. After drying, first heat to 220 °C at 2 °C / min under a nitrogen atmosphere and hold for 25 min, then switch to a hydrogen atmosphere and heat to 400 °C and hold for 50 min to obtain pre-coated powder.

[0055] Step 3: Add all the pre-coated powder obtained in Step 2 to a mixture of 4000 mL deionized water and 1200 mL anhydrous ethanol; add 0.7 g ammonium metavanadate to 130 mL deionized water, heat to 75°C, and then add 1.0 mL of 25% ammonia solution dropwise until completely dissolved. Add the suspension over 10 min and continue stirring for 30 min; separately dissolve 22 g nickel nitrate hexahydrate and 16 g sodium citrate dihydrate in 300 mL deionized water, and then add the mixture to a mixture of 4000 mL deionized water and 1200 mL anhydrous ethanol. The addition was completed within 0 min, and then 10% ammonia water was slowly added dropwise over 55 min until the pH of the system reached 8.8. The system was then kept at 55℃ for 75 min. After filtration, the system was washed once each with 500 mL of deionized water and 500 mL of anhydrous ethanol, and dried at 85℃ for 10 h. After drying, the system was first heated to 220℃ at 2℃ / min under a nitrogen atmosphere and kept at that temperature for 25 min, and then heated to 440℃ under a hydrogen atmosphere and kept at that temperature for 60 min to obtain the composite modified powder.

[0056] Step 4: Mix all the composite modified powder obtained in Step 3 with 0.60g of vanadium carbide (average particle size 1.5μm) and 900mL of anhydrous ethanol. Perform low-energy ball milling for 1.5h using cemented carbide balls at a ball-to-material ratio of 2:1 and a rotation speed of 140r / min. After ball milling, dry under reduced pressure at 60℃ for 4h. Then, add the mixture to a ball mill jar along with 50g of cobalt powder (average particle size 350nm), 1.4g of chromium carbide (average particle size 1.2μm), 0.45g of graphite powder (average particle size 1.4μm), 10g of paraffin wax, 4g of polyethylene glycol, and 650mL of anhydrous ethanol. Wet mill using cemented carbide balls for 8h at a ball-to-material ratio of 5:1 and a rotation speed of 200r / min. After ball milling, dry under reduced pressure at 56℃ and granulate through a 60-mesh sieve to obtain the pressed material.

[0057] Step 5: Press the pressed material obtained in Step 4 into a CNC turning tool blank. First, pre-press it at 100MPa, then final press it at 210MPa and hold the pressure for 40s. Then place it in a vacuum sintering furnace and heat it according to the following schedule under a vacuum degree not higher than 5Pa: 200℃ for 1h, 480℃ for 1h, 620℃ for 1h, 900℃ for 30min, 1278℃ for 15min; then heat it to 1388℃ and hold it for 45min to complete sintering. Then cool it with the furnace. Perform conventional grinding and edge passivation on the sintered tool. The edge passivation amount is controlled to be 20μm to obtain a high-strength and tough ultra-fine grain cemented carbide CNC tool.

[0058] Comparative Example 1:

[0059] The difference between Comparative Example 1 and Example 1 is that in step 1, the activation solution was prepared with only 2000 mL of deionized water, and 40% hydrofluoric acid, 65% nitric acid and ammonium fluoride were not added; the other conditions were the same as in Example 1.

[0060] Comparative Example 2:

[0061] The difference between Comparative Example 2 and Example 1 is that: in step 2, 15g of ferric nitrate nonahydrate is not added; in step 4, the cobalt powder is adjusted from 45g to 47.1g to make up the total metal content; the other conditions are the same as in Example 1.

[0062] Comparative Example 3:

[0063] The difference between Comparative Example 3 and Example 1 is that: in step 3, 24g of nickel nitrate hexahydrate and 12g of sodium citrate dihydrate are not added; in step 4, the cobalt powder is adjusted from 45g to 49.8g to make up the total metal content; the other conditions are the same as in Example 1.

[0064] Comparative Example 4:

[0065] The difference between Comparative Example 4 and Example 1 is as follows: In step 3, 24g of nickel nitrate hexahydrate and 12g of sodium citrate dihydrate were first dissolved in 300mL of deionized water and added dropwise over 40min. Then, 10% ammonia solution was slowly added dropwise over 50min until the pH of the system reached 8.7. After maintaining the temperature at 50℃ for 60min, 0.6g of ammonium metavanadate solution was added and stirring was continued for 30min. The remaining conditions were the same as in Example 1.

[0066] Comparative Example 5:

[0067] The difference between Comparative Example 5 and Example 1 is that: in step 3, 0.6g of ammonium metavanadate is not added; in step 4, vanadium carbide is adjusted from 0.5g to 0.82g so that the total amount of vanadium added is basically the same as in Example 1; the other conditions are the same as in Example 1.

[0068] Comparative Example 6:

[0069] The difference between Comparative Example 6 and Example 1 is that: in step 4, 0.5g of vanadium carbide is not added; in step 3, ammonium metavanadate is adjusted from 0.6g to 1.53g so that the total amount of vanadium added is basically the same as in Example 1; the other conditions are the same as in Example 1.

[0070] Comparative Example 7:

[0071] The difference between Comparative Example 7 and Example 1 is that in step 3, 1.5g of chromium carbide and 0.6g of ammonium metavanadate are added simultaneously to the suspension containing all the pre-coated powder obtained in step 2; in step 4, 1.5g of chromium carbide is not added; the other conditions are the same as in Example 1.

[0072] Performance testing:

[0073] Sample Preparation: The pressed materials obtained from Examples 1-5 and Comparative Examples 1-7 were used to prepare CNC turning insert blanks, and block and strip samples were simultaneously pressed. The block samples were uniformly 10mm × 10mm × 4mm in size and were used for density, magnetic property testing, and Rockwell hardness testing. The transverse fracture strength samples were uniformly 3mm × 4mm × 35mm in size, and the room temperature impact toughness samples were uniformly 5mm × 5mm × 35mm in size. All block and strip samples were prepared using the same dewaxing and sintering process as the corresponding inserts. The inserts used for cutting performance evaluation were uniformly ground into CNMG120408 external turning inserts after sintering, with a uniform tip radius of 0.8mm, and then uniformly passivated to 15μm to eliminate the influence of differences in cutting edge morphology on the comparative results. The grinding parameters, clamping methods, testing equipment, testing environment, and judgment criteria for each sample were kept consistent.

[0074] Test item 1: Density

[0075] The procedure was performed according to GB / T 3850-2015. Five block samples were taken from each group of samples. The samples were first kept in a drying oven at 110℃ for 1 hour, then cooled to room temperature, and the dried mass m1 was measured. The samples were then immersed in degassed distilled water at 23±1℃ for 30 minutes, and the mass of the immersion solution m2 was measured. The density was calculated using the Archimedes method, with the formula ρ = m1 × ρ. 水 / (m1-m2), where ρwater is the density of water at 23℃; each sample is tested 3 times, and the arithmetic mean is taken as the density result of the sample, and three decimal places are retained.

[0076] Test Item 2: Rockwell Hardness

[0077] The test was conducted according to GB / T 3849.1-2015. Three block-shaped specimens were taken from each group of samples. After being ground smooth by 1200#, 2000# and 3000# sandpaper, they were polished to a mirror finish with 1μm diamond polishing agent. The test was conducted using an A-scale diamond indenter with a main load of 60kgf. Ten points were measured on each specimen at a distance of not less than 1.5mm from each other and not less than 2mm from the edge. The highest and lowest values ​​were removed, and the average value was taken. The average value of the three specimens was then taken as the HRA result of the sample.

[0078] Test item 3: Transverse fracture strength

[0079] The test was conducted according to GB / T 3851-2015. Five rectangular specimens (3mm × 4mm × 35mm) were taken from each sample group. After surface grinding, a three-point bending test was performed. The support span was uniformly 30mm, and the loading speed was uniformly 0.5mm / min. The fracture load P was recorded and calculated using the formula σTRS = 3PL / (2bh). 2Calculate the transverse fracture strength, where L is 30 mm, b is the specimen width, and h is the specimen thickness; obtain at least 5 valid fracture data for each group of samples, and take the arithmetic mean as the transverse fracture strength result of the sample.

[0080] Test Item 4: Room Temperature Impact Toughness

[0081] The test was conducted according to GB / T 1817-2017. Five strip specimens with dimensions of 5mm×5mm×35mm were taken from each group of samples. After the surface of the specimens was finely ground, a room temperature impact test was performed. The pendulum energy was uniformly set to 15J and the support span was uniformly set to 30mm. The impact absorption energy K of each specimen was recorded, and the room temperature impact toughness aK = K / S was calculated based on the effective cross-sectional area S of the specimen. Each group of samples was tested 5 times, and the average value was taken as the room temperature impact toughness result of the sample.

[0082] Test Item 5: Magnetic Saturation

[0083] The test shall be conducted in accordance with GB / T 23369-2009. Three block specimens shall be taken for each group of samples. After the specimen surfaces are ground smooth and cleaned, they shall be tested using a cemented carbide magnetic saturation tester at 20±2℃. Before the test, the test shall be calibrated with a standard specimen. Each specimen shall be measured three times, and the average value shall be taken as the result of a single specimen. The average value of the three specimens shall be taken as the magnetic saturation result of the sample.

[0084] Test item six: Coercive magnetic force

[0085] The test was conducted according to GB / T 3848-2017. Three block specimens were taken from each group of samples, with a uniform size of 10mm×10mm×4mm. After removing the grinding oxide layer and wiping the surface clean, the specimens were tested using a cemented carbide coercivity tester at 20±2℃. Each specimen was tested three times consecutively, and the average value was taken as the result of a single specimen. The average value of the three specimens was then taken as the coercivity result of the sample.

[0086] Test item seven: Continuous turning life of 42CrMo

[0087] The process was conducted according to GB / T 16461-2016. The workpiece material was 42CrMo steel. The outer diameter of the samples was uniformly 90mm, and the length was uniformly 300mm. After tempering, the hardness was controlled between 32-36HRC. Before cutting, the surface roughness of the outer diameter of the workpiece was controlled below Ra 1.6μm. The cutting tool was mounted on a 25mm×25mm outer diameter turning tool holder with a uniform overhang length of 35mm. Dry cutting was used, with a uniform cutting speed of 180m / min, a uniform feed rate of 0.18mm / r, and a uniform depth of cut of 1.0mm. The machine was stopped every 30 seconds of cumulative cutting. The maximum flank wear width VBmax and the maximum micro-chipping width were measured using a tool microscope. The tool was considered to have failed when VBmax reached 0.20mm, the maximum micro-chipping width reached 100μm, or the cutting tool experienced sudden breakage. Three cutting tools were tested for each sample, and the average effective cutting time was taken as the tool life of that sample under continuous turning conditions on 42CrMo steel.

[0088] Test Item 8: H62 Semi-Intermittent Turning Life

[0089] The test was conducted according to GB / T 16461-2016. The workpiece material was H62 copper alloy. The outer diameter of the samples was uniformly 80 mm, and the length was uniformly 250 mm. Four axial grooves were evenly machined around the outer circumference of the workpiece, each groove being 6 mm wide and 2 mm deep to create a stable semi-interrupted cutting condition. The tool installation method was the same as in test item seven, using dry cutting with a uniform cutting speed of 320 m / min, a uniform feed rate of 0.12 mm / r, and a uniform depth of cut of 0.5 mm. The machine was stopped once every 1 minute of cumulative cutting, and the maximum flank wear width VBmax and the maximum micro-chipping width were measured using a tool microscope. The tool was considered to have failed when VBmax reached 0.15 mm, the maximum micro-chipping width reached 80 μm, or the tool experienced sudden breakage. Three tools were tested for each sample, and the average effective cutting time was taken as the tool life of that sample under the H62 semi-interrupted turning condition.

[0090] Table 1 Performance test results of the examples and comparative examples

[0091] sample <![CDATA[Density / (g / cm 3 )]]> Rockwell hardness (HRA) Transverse fracture strength (MPa) <![CDATA[Charpy impact toughness at room temperature / (kJ / m 2 )]]> Magnetic saturation / (%) Coercivity (kA / m) Continuous turning life of 42CrMo (min) H62 semi-interrupted turning life (min) Example 1 14.446 92.5 3818 29.4 80.8 22.9 17.6 32.8 Example 2 14.552 92.7 3567 25.8 81.4 23.4 15.9 28.6 Example 3 14.347 92.1 3906 31.2 79.9 21.6 16.8 34.6 Example 4 14.531 92.8 3679 27.1 80.5 24.0 18.1 30.9 Example 5 14.369 91.9 3752 30.0 80.1 21.0 15.8 35.4 Comparative Example 1 14.392 91.4 3008 20.6 82.3 18.9 10.8 19.6 Comparative Example 2 14.431 91.8 3336 24.3 80.2 21.4 13.8 24.9 Comparative Example 3 14.428 91.7 3217 22.1 81.8 20.8 12.6 21.8 Comparative Example 4 14.435 91.9 3388 23.9 80.3 21.8 14.2 25.6 Comparative Example 5 14.424 92.3 3407 22.8 80.6 22.1 14.7 23.7 Comparative Example 6 14.441 92.0 3358 24.8 80.0 21.3 13.9 26.2 Comparative Example 7 14.430 92.1 3446 23.4 80.4 21.9 14.9 24.6

[0092] Data Analysis:

[0093] As can be seen from the data in the table of examples, the high-strength and tough ultrafine-grained cemented carbide CNC inserts prepared by this invention maintain a good matching relationship between density, Rockwell hardness, transverse fracture strength, room temperature impact toughness, magnetic properties, and two types of turning life. This indicates that the process does not rely on the addition or subtraction of a single component to achieve local improvement, but rather achieves this by first activating ultrafine tungsten carbide powder, then sequentially forming an iron-based enriched inner layer, undergoing ammonium metavanadate treatment to form a nickel-based enriched outer layer, and subsequently adding vanadium carbide and chromium carbide in stages, along with initial pre-heating in the liquid phase. This results in a sintered microstructure with a high degree of densification, a relatively uniform distribution of the binder phase, and a relatively stable grain boundary state. Therefore, this insert exhibits good resistance to flank wear in continuous turning of 42CrMo, and also maintains resistance to micro-chipping in semi-interrupted turning of H62, demonstrating a simultaneous improvement in wear resistance and toughness.

[0094] As can be seen from the data in Example 1 and Comparative Example 1, after simply removing the activation treatment consisting of hydrofluoric acid, nitric acid, and ammonium fluoride, the density, Rockwell hardness, transverse fracture strength, room temperature impact toughness, and both types of turning life of the samples all decreased significantly, and the magnetic saturation shifted upward and the coercivity decreased. The main reason for this is that the unactivated ultrafine tungsten carbide powder has insufficient surface defect sites, making it difficult to stably construct the subsequent iron-based enriched inner layer and nickel-based enriched outer layer. The interaction sites of ammonium metavanadate, vanadium carbide, and chromium carbide are also more dispersed, making grain growth and binder phase migration more likely to occur during sintering.

[0095] As can be seen from the data in Example 1 and Comparative Example 2, when the iron-based enriched inner layer formed by ferric nitrate nonahydrate is missing, although the sample still maintains a certain density and hardness, the transverse fracture strength, room temperature impact toughness, and H62 semi-interrupted turning life are all reduced. The main reason is that the iron-based enriched inner layer can improve the reaction basis of the activated tungsten carbide surface and provide more uniform interface conditions for the subsequent formation of the nickel-based enriched outer layer. Without this inner layer, the continuity of the binder phase distribution decreases, and local stress concentration is more likely to occur near the cutting edge, thus the resistance to micro-chipping is more significantly impaired.

[0096] As can be seen from the data in Example 1 and Comparative Example 3 in the table, the transverse fracture strength, room temperature impact toughness, and H62 semi-interrupted turning life of the samples decreased more significantly when the nickel-based enriched outer layer was missing. The main reason is that the nickel-based enriched outer layer is closer to the region where the final binder phase participates, which helps to alleviate interfacial stress concentration and improve the uniformity of the binder phase after sintering. Without this outer layer, a fragile area is more likely to form near the cutting edge, making it easier to induce micro-chipping under semi-interrupted impact loading.

[0097] As can be seen from the data in Example 1 and Comparative Example 4 in the table, simply changing the order in which ammonium metavanadate and the nickel-based enriched outer layer are introduced simultaneously reduces the Rockwell hardness, transverse fracture strength, and both types of turning life of the samples. This indicates that the key to this invention lies not only in whether each component is added, but also in the order in which they are added. When ammonium metavanadate is added first, it is more conducive to forming a uniform initial confinement effect on the surface of the pre-coated powder, and then the nickel-based enriched outer layer covers and stabilizes the interface; if the nickel-based enriched outer layer is formed first, and then ammonium metavanadate is added, it is more difficult for the vanadium source to play a role in the appropriate position, thereby weakening the subsequent successive effect of vanadium carbide and chromium carbide.

[0098] As can be seen from the data in Examples 1, 5, and 6 of the table, when only vanadium carbide is retained and ammonium metavanadate is removed, the samples tend to maintain surface wear resistance, but the transverse fracture strength, room temperature impact toughness, and H62 semi-interrupted turning life decrease. When only ammonium metavanadate is increased and vanadium carbide is removed, the samples tend to maintain a certain degree of chipping resistance, but the 42CrMo continuous turning life and fine grain stability are insufficient. The main reason is that ammonium metavanadate is more suitable for front-end interface confinement, while vanadium carbide is more suitable for back-end grain boundary suppression. Only when the two are in different stages can grain coarsening be suppressed simultaneously and local embrittlement caused by excessive concentration of a single vanadium source be avoided.

[0099] As can be seen from the data in Example 1 and Comparative Example 7, when chromium carbide is added at the same stage as ammonium metavanadate, although the sample can still maintain a certain hardness, its transverse fracture strength, room temperature impact toughness, and both types of turning life are inferior to those of Example 1. The main reason is that chromium carbide is more suitable as a post-component in this invention. After being wet-milled together with cobalt powder, it can play a greater role in the peripheral area of ​​the interface and the stability of the microstructure in the later stage of sintering. If it is added too early, it is easy to interfere with the timing coordination of the iron-based enriched inner layer, the ammonium metavanadate treatment, and the nickel-based enriched outer layer, weakening the overall stepwise construction effect.

[0100] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A high-strength, high-toughness, ultra-fine-grained cemented carbide CNC cutting tool, characterized in that, The blade substrate includes a high-strength, high-toughness, ultrafine-grained cemented carbide material. By mass, the high-strength, high-toughness, ultrafine-grained cemented carbide material is prepared from the following raw materials: 500 parts of ultrafine tungsten carbide powder with an average particle size of 80-150 nm as the substrate, which is first activated to form an iron-based enriched inner layer and then treated with ammonium metavanadate to form a nickel-based enriched outer layer, 40-50 parts of cobalt powder, 0.35-0.70 parts of vanadium carbide, 1.2-1.8 parts of chromium carbide, and 0.3-0.5 parts of graphite powder.

2. The high-strength, high-toughness, ultra-fine-grained cemented carbide CNC cutting tool according to claim 1, characterized in that, The activation is carried out using an acid-ammonium fluoride system activation solution composed of hydrofluoric acid, nitric acid and ammonium fluoride.

3. The high-strength, high-toughness, ultra-fine-grained cemented carbide CNC cutting tool according to claim 2, characterized in that, The activation solution is prepared by mixing deionized water, hydrofluoric acid with a mass fraction of 40%, nitric acid with a mass fraction of 65%, and ammonium fluoride in a ratio of 1900-2200mL:55-70mL:35-50mL:5-8g.

4. The high-strength and tough ultra-fine-grained cemented carbide CNC cutting tool according to claim 1, characterized in that, The composite modified ultrafine tungsten carbide powder is prepared from the following raw materials: based on 500 parts of ultrafine tungsten carbide powder with an average particle size of 80-150 nm, 12-18 parts of ferric nitrate nonahydrate, 0.4-0.8 parts of ammonium metavanadate and 20-28 parts of nickel nitrate hexahydrate are added.

5. The high-strength, high-toughness, ultra-fine-grained cemented carbide CNC cutting tool according to claim 1, characterized in that, The cobalt powder has an average particle size of 350 nm, the vanadium carbide has an average particle size of 1.5 μm, the chromium carbide has an average particle size of 1.2 μm, and the graphite powder has an average particle size of 1.4 μm.

6. The high-strength, high-toughness, ultra-fine-grained cemented carbide CNC cutting tool according to claim 1, characterized in that, The CNC cutting tool undergoes edge passivation treatment, with a passivation amount of 12-20μm.

7. A manufacturing process for a high-strength, high-toughness, ultra-fine-grained cemented carbide CNC cutting tool according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Activate the ultrafine tungsten carbide powder to obtain activated tungsten carbide powder; S2. The activated tungsten carbide powder is deposited with an iron source and reduced to obtain a pre-coated powder with an iron-based enriched inner layer on the surface. S3. The pre-coated powder is treated with ammonium metavanadate, then nickel source is deposited and reduced to obtain the composite modified ultrafine tungsten carbide powder. S4. The composite modified ultrafine tungsten carbide powder is mixed with vanadium carbide and then subjected to low-energy ball milling. After drying, it is mixed with cobalt powder, chromium carbide and graphite powder, wet-milled, dried and granulated to obtain pressed material. S5. After pressing the material into a blade blank, sinter it, and then grind and passivate the sintered blade to obtain a high-strength and tough ultra-fine grain cemented carbide CNC blade.

8. The manufacturing process of the high-strength and tough ultra-fine grain cemented carbide CNC cutting tool according to claim 7, characterized in that, The reduction in step S2 is as follows: first, the temperature is increased to 190-220℃ at 2℃ / min under a nitrogen atmosphere and held for 20-25min, then the temperature is increased to 370-400℃ under a hydrogen atmosphere and held for 35-50min; the reduction in step S3 is as follows: first, the temperature is increased to 190-220℃ at 2℃ / min under a nitrogen atmosphere and held for 20-25min, then the temperature is increased to 410-440℃ under a hydrogen atmosphere and held for 45-60min.

9. The manufacturing process of the high-strength and tough ultra-fine grain cemented carbide CNC cutting tool according to claim 7, characterized in that, In step S4, the low-energy ball milling time is 0.8-1.5h, the ball-to-material ratio is 2-4:1, and the rotation speed is 110-140r / min; the wet milling time is 5-8h, the ball-to-material ratio is 5-6:1, and the rotation speed is 170-200r / min.

10. The manufacturing process of the high-strength and tough ultra-fine grain cemented carbide CNC cutting tool according to claim 7, characterized in that, In step S5, during pressing, the material is first pre-pressed at 70-100MPa, then finally pressed at 170-210MPa and held for 25-40 seconds. During sintering, the temperature is increased according to the following regime under a vacuum degree not exceeding 5Pa: 200℃ for 1 hour, 480℃ for 1 hour, 620℃ for 1 hour, 900℃ for 25-35 minutes, 1270-1290℃ for 12-20 minutes, and then increased to 1380-1400℃ for 35-45 minutes.